Piston, method of construction, and piston body portions thereof

ABSTRACT

A method of constructing a piston, piston formed thereby, and piston body portions are provided. The method includes providing an upper crown portion at least one annular upper rib depending from the upper combustion wall to a free end having a tapered peak. The method further includes providing a lower crown portion having at least one annular lower rib extending to a free end having a tapered peak. Then, moving the upper crown portion and the lower crown portion toward one another and initiating contact between the upper crown portion and the lower crown portion at their respective tapered peaks. Then, continuing moving the upper crown and the lower crown further toward one another after making initial contact at their respective tapered peaks and forming a friction weld joint between the free ends of the at least one upper rib and the at least one lower rib free end.

CROSS-REFERENCE TO CO-PENDING APPLICATION

This U.S. Divisional Application claims the benefit of U.S. Continuationapplication Ser. No. 13/677022, filed Nov. 14, 2012, which claims thebenefit of U.S. application Ser. No. 12/646,227, filed Dec. 23, 2009,both of which are incorporated herein by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Technical Field

This invention relates generally to pistons for internal combustionengines, and more particularly to pistons having an oil cooling gallery.

2. Related Art

Piston constructions having two substantially closed oil coolinggalleries are known. These pistons have an annular, radially outergallery and an open central gallery formed between upper and lower crownportions. The outer and central galleries can be isolated from oneanother or in fluid communication with one another via oil passages. Inaddition, it is known to provide pin lubrication passages extending fromone or both of the galleries to a wrist pin. The lubrication passagescan extend into a wrist pin bore of a pin boss and/or between laterallyspaced pin bosses. The outer gallery is particularly effective incooling a ring belt region of the piston, while the central gallery isparticularly effective in cooling a central crown region formed in partby a combustion bowl wall, which is exposed to hot combustion gasses.

Aside from the combustion bowl being exposed to extreme heat, it is alsoexposed to extreme combustion forces. Accordingly, the combustion bowlwall needs to withstand the extreme combustion forces. With the centralcavity being open beneath the combustion bowl wall, there is anunsupported central region of the combustion bowl wall directly abovethe central gallery. As such, the central region attains its structuralsupport from a radially outer annular wall formed between the outer andcentral galleries. Accordingly, both the central region of thecombustion bowl and the annular wall must be constructed having asuitable thickness and configuration to withstand the combustion forcesgenerated in use.

SUMMARY OF THE INVENTION

A method of constructing a piston is provided. The method includesproviding an upper crown portion having an upper combustion wall againstwhich combustion forces directly act in the cylinder bore and at leastone annular upper rib depending from the upper combustion wall to a freeend having a tapered peak. Further, providing a lower crown portionhaving at least one annular lower rib extending to a free end having atapered peak and a pair of pin bosses configured for receipt of a smallend of a connecting rod therebetween. The method further includes movingthe upper crown portion and the lower crown portion toward one anotherand initiating contact between the upper crown portion and the lowercrown portion at their respective tapered peaks, and then, continuingmoving the upper crown and the lower crown further toward one anotherafter making initial contact at their respective tapered peaks andforming a friction weld joint between the free ends of the at least oneupper rib and the at least one lower rib free end.

In accordance with a further aspect of the invention, the method furtherincludes providing the upper crown portion with a pair of annular upperribs depending from the upper combustion wall, one being an upper innerrib extending to a free end and the other being an upper outer ribextending to a free end having a tapered peak, and providing the lowercrown with a pair of annular lower ribs, one being a lower inner ribbounding an inner gallery floor and extending to a free end and theother being a lower outer rib extending to a free end having a taperedpeak. The method further includes moving the upper crown portion and thelower crown portion toward one another and initiating contact of theupper and lower outer ribs at their respective tapered peaks, and then,forming a friction weld joint between the upper outer rib free end andthe lower outer rib free end.

In accordance with a further aspect of the invention, the method furtherincludes maintaining the upper inner rib free end and the lower innerrib free end in spaced relation from one another to form an annular gaptherebetween.

In accordance with a further aspect of the invention, the method furtherincludes providing the upper and lower inner ribs with tapered peaks andinitiating contact of the upper and lower inner ribs at their respectivetapered peaks while moving the upper crown portion and the lower crownportion toward one another, and then, forming a friction weld jointbetween the upper inner rib free end and the lower inner rib free end.

In accordance with a further aspect of the invention, piston bodyportions configured for fixation to one another to form a piston areprovided. The piston body portions include an upper crown portion and alower crown portion. The upper crown portion has an upper combustionwall and at least one annular upper rib depending from the uppercombustion wall to a free end having a tapered peak. The lower crownportion has at least one annular lower rib extending to a free endhaving a tapered peak and further including a pair of pin bossesconfigured for receipt of a small end of a connecting rod therebetween.The tapered peak of the at least one annular upper rib is configured foraxial alignment and contact with the tapered peak of the at least oneannular lower rib.

In accordance with a further aspect of the invention, the free end ofthe at least one annular upper rib and the free end of the at least oneannular lower rib are substantially mirror images of one another.

In accordance with a further aspect of the invention, the upper crownportion has a pair of the annular upper ribs with each having free endswith tapered peaks and wherein the lower crown portion has a pair of theannular lower ribs with each having free ends with tapered peaks. Thetapered peaks of the upper crown portion are configured for axialalignment and contact with the tapered peaks of the lower crown portion.

In accordance with a further aspect of the invention, the free ends ofthe pair of annular upper ribs and the free ends of the pair of annularlower ribs are substantially mirror images of one another.

In accordance with another aspect of the invention, a piston isprovided. The piston includes a piston body having an upper crownportion and a lower crown portion. The upper crown portion has an uppercombustion wall and a pair of annular upper ribs depending from theupper combustion wall. One of the annular upper ribs is an upper innerrib extending to a free end and the other of the annular upper ribs isan upper outer rib extending to a free end. The lower crown portion hasa pair of annular lower ribs. One of the annular lower ribs is a lowerinner rib extending to a free end and the other of the annular lowerribs is a lower outer rib extending to a free end. The lower crownportion further includes an inner gallery floor arranged radiallyinwardly from the annular lower inner rib and a pair of pin bossesdepending generally from the inner gallery floor with a space providedbetween the pin bosses for receipt of a small end of a connecting rod.An annular outer cooling gallery is formed between the inner and outerribs of the upper and lower crown portions and an annular centralcooling gallery is formed radially inwardly from the inner ribs of theupper and lower crown portions. The inner ribs of the upper and lowercrown portions are spaced axially from one another to provide an annularoil gap extending between the outer cooling gallery and the centralcooling gallery.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, features and advantages of the invention willbecome more readily appreciated when considered in connection with thefollowing detailed description of presently preferred embodiments andbest mode, appended claims and accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a piston constructed in accordancewith one presently preferred aspect of the invention;

FIG. 1A is a view of the piston of FIG. 1 shown prior to forming anyfriction weld joints between an upper and lower crown portion thereof;

FIG. 2 is a cross-sectional view of a piston constructed in accordancewith another aspect of the invention;

FIG. 3 is a cross-sectional view of a piston constructed in accordancewith yet another aspect of the invention;

FIG. 3A is a view of the piston of FIG. 3 shown prior to forming anyfriction weld joints between an upper and lower crown portion thereof;and

FIG. 4 is a cross-sectional view of a piston constructed in accordancewith yet another aspect of the invention.

DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS

Referring in more detail to the drawings, FIG. 1 illustrates a piston 10constructed in accordance with one presently preferred aspect of theinvention. The piston 10 has a piston body 12, such as preferablyconstructed of steel, although other material are contemplated to bewithin the scope of the invention, extending along a central axis 14along which the piston body reciprocates within a cylinder bore (notshown). The piston body 12 includes an upper crown portion 16 having anupper combustion wall 18, represented here, by way of example andwithout limitation, as providing a recessed combustion bowl 20, againstwhich combustion forces directly act in the cylinder bore. The uppercrown portion 16 has at least one, and shown here as a pair of annularupper inner ribs, referred to hereafter as an upper inner rib 22 andupper outer rib 24, depending from the upper combustion wall 18 torespective free ends 26, 28. The piston body 12 further includes a lowercrown portion 30 having at least one, and shown here as a pair ofannular lower ribs, referred to hereafter as a lower inner rib 32 andlower outer rib 34, extending to respective free ends 36, 38 arranged inalignment for engagement with the free ends 26, 28. The lower crownportion 30 further includes an inner gallery floor 40 arranged radiallyinwardly from the lower inner rib 32 and a pair of pin bosses 42, 44depending generally from the inner gallery floor 40 with a space 46provided between the pin bosses 42, 44 for receipt of a small end of aconnecting rod (not shown). In addition, the upper crown portion 16and/or the lower crown portion 30, and shown here as both, have arespective central support post 48, 50 extending along the central axis14 to respective free ends 52, 54. In accordance with a method ofconstructing the piston 10, an initial step includes initiating afriction weld joint 56 between the free ends 52, 54 of the upper andlower central support posts 48, 50. Then after initiating the frictionweld joint 56, a subsequent step includes forming friction weld joints58, 60 between the respective upper and lower inner rib free ends 26, 36and the upper and lower outer rib free ends 28, 38 and then completingthe friction weld joint 56 between the central support member free ends52, 54.

The upper crown portion 16 can be constructed having oil flow passagesto facilitate cooling the piston, and is shown here as having a pair ofoil flow passages 62 extending through the upper inner rib 22. The oilflow passages 62 are formed having a slightly ascending attitudeextending from the central axis 14 radially outwardly, The location,geometry and angle of the oil flow passages 62 can be varied dependingon the size of the oil gallery and the availability/volume of oil. Theupper crown portion 16 is formed having an annular outer oil gallerypocket 64 extending from the inner and outer rib free ends 26, 28upwardly into an upper ring belt region 66 and adjacent the uppercombustion wall 18. The upper crown portion 16 is also formed having anannular inner oil gallery pocket 68 extending from the inner free end 26and the central support post free end 52 upwardly and immediatelybeneath the combustion bowl 20. As shown in FIG. 1A, prior to fixing theupper crown portion 16 to the lower crown portion 30, the upper centralsupport post free end 52 is provided having an end 69, such as atapered, spherical, conical or pyramidal shape, by way of example andwithout limitation, and the lower central support post free end 54 isprovided having an end 81, such as a tapered, spherical, conical orpyramidal shape, by way of example and without limitation.

The lower crown portion 30 can be constructed having oil flow passagesto facilitate cooling the piston, and is shown here as having a T-shapedcentral oil flow passage 70 extending partially along the central axis14, and thus, partially through the central support post 50. The oilflow passage 70 also has a cross opening 71 formed extending generallyperpendicularly to the central axis 14 through the central support post50. The oil flow passage 70 facilitates lubricating a wrist pin (notshown) that is received through the pin bores 72 in the pin bosses 42,44. The lower crown portion 30 is formed having an annular outer oilgallery pocket 74 extending from the inner and outer rib free ends 36,38 downwardly into a lower ring belt region 76. The lower crown portion30 is also formed having an annular inner oil gallery pocket 78extending from the inner free end 36 and the central support post freeend 54 downwardly. in addition, an oil flow passage 80, such asdisclosed in U.S. Pat. No. 6,477,941, which is incorporated herein byreference in its entirety, is formed extending from one of the pin bores72 upwardly into the bottom of the outer oil gallery pocket 74. As such,oil is pumped from the pin bore 72 upwardly into the outer oil gallerypocket 74 (the oil can be pumped via oil cooling jet nozzles, notshown), circulated about the outer oil gallery pockets 64, 74, whichcombine to form a single outer oil gallery, and channeled inwardlythrough the oil flow passages 62 into the inner oil gallery pockets 68,78, circulated through the inner oil gallery pockets 68, 78, whichcombine to form a single inner oil gallery, and channeled through thecross opening 71 and the oil flow passage 70 centrally onto the wristpin to facilitate lubricating the wrist pin and small end of theassociated connecting rod.

The method of construction, as mentioned above, involves a two stepprocess, which includes a first step of initiating the friction weldjoint 56 between the axially aligned central support posts 48, 50 priorto a second step, which includes initiating the friction weld joints 58,60 between the inner rib free ends 26, 36 and the outer rib free ends28, 38. While initiating the friction weld joint between the ends 69, 81of the upper and lower central support posts 48, 50, the upper and lowercrown portions 16, 30 are rotated relative to one another at a first,high rotational velocity. As shown in FIG. 1A, as the ends 69, 81initially contact one another, the inner rib free ends 26, 36 and theouter rib free ends 28, 38 remain spaced axially from one another by adistance Y, and thus, the friction welding does not begin in thisregion. This allows the central support posts 48, 50 to begin meltingprior to the initiating melting of the inner rib free ends 26, 36 andthe outer rib free ends 28, 38. This in necessary to establish a goodfriction weld at the central support post 48, 50 due to the differencein rotational velocity between in inner central region, which isrelatively slow in comparison to the rotational velocity at radiallyoutward regions. After the friction weld has begun to become establishedbetween the central support posts 48, 50, the ends 69,81. diminish inheight, such as by, a distance X, wherein X is substantially equal tothe distance Y, thereby eliminating the space between the inner rib freeends 26, 36 and the outer rib free ends 28, 38 and thus, bring the innerrib free ends 26, 36 and the outer rib free ends 28, 38 into frictionalcontact with one another. This begins the second step of initiating thefriction weld joints 58, 60 between the inner rib free ends 26, 36 andthe outer rib free ends 28, 38 and then completing the weld joints 56,58, 60.

In FIG. 2, a piston 110 is shown in accordance with another aspect ofthe invention, wherein the same reference numerals as used above, offsetby a factor of 100, are used to identify like features. The piston 110has an upper crown portion 116 friction welded to a lower crown portion130 using a similar two step welding process as discussed above, whereinthe friction welding process is first initiated between a pair ofaxially aligned central support posts 148, 150, and then, free ends 128,138 of upper and lower outer ribs 124, 134 are friction welded together.However, unlike the prior embodiment, the piston 110 does not frictionweld a pair of upper and lower inner ribs 122, 132 together, but rather,maintains a space between the upper and lower inner ribs 122, 132 toprovide an annular oil gap 90 extending between an outer cooling gallery91 and a central cooling gallery 93. Accordingly, the oil within theouter cooling gallery 91 has a readily accessible, continuous annularpath through which to flow into the central cooling gallery 93, therebyfacilitating uniform cooling of the piston body 112 while avoidingpooling of oil, and thus, avoiding heating of pooled oil within therespective cooling galleries. It should be recognized that the thicknessof the annular oil gap 90, along the axial direction, can be providedhaving a range of thickness, as desired. For example, if the annular oilgap 90 is desired to be relatively narrow, then the axial gap betweenthe upper and lower outer ribs 124, 134 will be less than that if thedesired annular oil gap 90 were desired to be relatively wide, andvise-versa. In addition, rather than providing an oil flow passagethrough the lower central support post 150, a pair of oil flow passages92, 94 can be formed through an inner gallery floor 140 above a centralportion of the wrist pin (not shown).

In FIG. 3, a piston 210 is shown in accordance with another aspect ofthe invention, wherein the same reference numerals as used above, offsetby a factor of 200, are used to identify like features. The piston 210has an upper crown portion 216 friction welded to a lower crown portion230 using a similar two step welding process as discussed above, whereinthe friction welding process is first initiated along an axially alignedcentral support post, however, rather than incorporating a pair ofaxially aligned central support posts, as with the previous pistons 10,110, the piston 210 has a single central support post 250 constructedentirely as a single piece of material with the lower crown portion 230,wherein the central support post 250 is friction welded directly to anunderside 96 of an upper combustion wall 218. As shown in FIG. 3A, thecentral support post 250 has a free end, represented as a free end,represented as a tapered free end 254, to facilitate the initial weldingstep, as discussed above. Also, the tapered free end 254 is providedhaving a length sufficient to engage the underside 96 of the uppercombustion wall 218 prior to frictional engagement resulting betweenfree ends 226, 236 of upper and lower inner ribs 222, 232 and betweenfree ends 228, 238 of upper and lower outer ribs 224, 234. Accordingly,for the same reasons discussed above, a friction weld joint 256 isinitiated between the central support post 250 and the underside 96 ofthe combustion wall 218 prior to initiating the respective friction weldjoints 258, 260 between the upper and lower inner ribs 222, 232 and theupper and lower outer ribs 224, 234. Of course, upon initiating the weldjoint 256 between the central support post 250 and the combustion wall218, at an increased first rotational velocity, the second step includesinitiating the friction weld joints 258, 260 between the upper and lowerinner ribs 222, 232 and the upper and lower outer ribs 224, 234 at areduced, second rotational velocity, as discussed above. Otherwise, thepiston 210 has an oil flow passage 280 extending from a pin bore to anannular outer oil gallery 291 and a pair of oil flow passages 292, 294extending through an inner gallery floor 240 into an annular central oilgallery 293.

In FIG. 4, a piston 310 is shown in accordance with another aspect ofthe invention, wherein the same reference numerals as used above, offsetby a factor of 300, are used to identify like features. The piston 310has an upper crown portion 316 friction welded to a lower crown portion330 using a similar two step welding process as discussed above, whereinthe friction welding process is first initiated along an axially alignedcentral support post 350, wherein the entire central support post 350 isconstructed as a single piece of material with the upper crown portion316. The central support post 350 is friction welded directly to aninner gallery floor 340 of the lower crown portion 330. As with theembodiment illustrated in FIG. 3A, prior to welding, the central supportpost 350 has a length sufficient to engage the inner gallery floor 340of the lower crown portion 330 prior to frictional engagement resultingbetween free ends 326, 336 of upper and lower inner ribs 322, 332 andbetween free ends 328, 338 of upper and lower outer ribs 324, 334.Accordingly, for the same reasons discussed above, a friction weld joint356 is initiated between the free end of the central support post 350and the inner gallery floor 340 of the lower crown portion 330 prior toinitiating the respective friction weld joints 358, 360 between theupper and lower inner ribs 322, 332 and the upper and lower outer ribs324, 334. Of course, upon initiating the weld joint 356 between thecentral support post 350 and the inner gallery floor 340, at anincreased first rotational velocity, the second step includes initiatingthe friction weld joints 358, 360 between the upper and lower inner ribs322, 332 and the upper and lower outer ribs 324, 334 at a reduced,second rotational velocity, as discussed above. Otherwise, the piston310 has an oil flow passage 380 extending from a pin bore to an annularouter oil gallery 391 and a pair of oil flow passages 392, 394 extendingthrough the inner gallery floor 340 radially outward from the centralpost 350 into an annular central oil gallery 393.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

What is claimed is:
 1. A method of constructing a piston, comprising:providing an upper crown portion having an upper combustion wall againstwhich combustion forces directly act in the cylinder bore and at leastone annular upper rib depending from the upper combustion wall to a freeend having a tapered peak; providing a lower crown portion having atleast one annular lower rib extending to a free end having a taperedpeak and a pair of pin bosses configured for receipt of a small end of aconnecting rod therebetween; moving the upper crown portion and thelower crown portion toward one another and initiating contact betweenthe upper crown portion and the lower crown portion at their respectivetapered peaks; and moving the upper crown and the lower crown furthertoward one another after making initial contact at their respectivetapered peaks and forming a friction weld joint between the free ends ofthe at least one upper rib and the at least one lower rib free end. 2.The method of claim 1 further including providing the upper crownportion with a pair of annular upper ribs depending from the uppercombustion wall, one being an upper inner rib extending to a free endand the other being an upper outer rib extending to a free end having atapered peak, and providing the lower crown with a pair of annular lowerribs, one being a lower inner rib bounding an inner gallery floor andextending to a free end and the other being a lower outer rib extendingto a free end having a tapered peak; moving the upper crown portion andthe lower crown portion toward one another and initiating contact of theupper and lower outer ribs at their respective tapered peaks; andforming a friction weld joint between the upper outer rib free end andthe lower outer rib free end.
 3. The method of claim 2 further includingmaintaining the upper inner rib free end and the lower inner rib freeend in spaced relation from one another to form an annular gaptherebetween.
 4. The method of claim 2 further including providing theupper and lower inner ribs with tapered peaks and initiating contact ofthe upper and lower inner ribs at their respective tapered peaks whilemoving the upper crown portion and the lower crown portion toward oneanother; and forming a friction weld joint between the upper inner ribfree end and the lower inner rib free end.